Bad geometry on mobile when mirroring

Hi there,

Can anyone give me some guidance why this is happening?
I have 2 window panes. They are identical. The issue only happens when testing on mobile and it seems to have something to do with mirroring.

I have tried:

  • mirroring in Unreal ( set x axis as -1 ) - same result
  • resetting xForm in Max - same result
  • I have checked normals - they seem good

I’m at my whits end.

Thanks in advance,